Lutfur Rahman has been found guilty of corrupt and illegal practices.
Photograph: Graeme Robertson

Police are considering whether to launch a criminal inquiry relating to the former mayor of Tower Hamlets after he was found guilty of multiple corruption allegations by the high court and kicked out of office.

The mayoral election in the east London borough will be rerun after Lutfur Rahman and his supporters were found to have used religious intimidation through local imams, vote-rigging and wrongly branding his Labour rival a racist to gain power.

Rahman, who has been banned from seeking office again, was also found to have allocated local grants to buy votes. He was ordered to pay immediate costs of £250,000 from a bill expected to reach £1m.

Summing up, Judge Richard Mawrey said Rahman had sought to play the “race and Islamophobia card” throughout the election and would no doubt do so after this judgment. “He was an evasive witness – Rahman was no doubt behind illegal and corrupt practices,” Mawrey said.

He also faces being stripped of his profession as a lawyer after the judge claimed he told “a pack of lies” in the witness box.

The ferocity of the judge’s verdict provoked gasps in court. Friends of Rahman claimed he had been unfairly treated.

Police on Thursday struggled to react to the judgment, based mainly on evidence put together by local voters. Last April, detectives examined allegations of electoral fraud and corruption against Rahman but found no evidence of criminal wrongdoing.

A Met statement last night said the force has noted the judgment and will consider the 200-page report.

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Rahman, who is no longer mayor and will be removed from the electoral roll, expressed shock at the judgment and said he was considering launching a judicial review – his only possible course of legal action.

A statement on his website said: “Today’s judgment has come as a shock – the mayor strongly denies any wrongdoing and had full confidence in the justice system, and so this result has been surprising to say the least.”

Even if he does challenge the ruling, he will not stop a new mayoral election, which is expected to be held in mid-June. Rahman is barred from standing again.

Outside the Royal Courts of Justice in central London, Biggs said the ruling was “a victory for honest politics”.

However, Ken Livingstone, the former London mayor, said he was “distinctly uncomfortable” with a court’s ability to remove an elected mayor. “If there is any illegality, then surely that’s a matter for the police.

“I’m uneasy that a mayor who has taken on the political powers in a borough can be removed by someone who is essentially a bureaucrat. What I don’t understand is why he [Mawrey] found evidence of corruption that the police have so far failed to identify,” he said.

The judge handed down his verdict on Thursday after a 10-week hearing at the Royal Courts of Justice.

A group of four residents – defined as petitioners by the election court – had called for last year’s mayoral election, in which Rahman triumphed over Labour rival John Biggs, to be declared void.

Mawrey said: “The evidence laid before this court, limited though it necessarily was to the issues raised in the petition, has disclosed an alarming state of affairs in Tower Hamlets.

“This is not the consequence of the racial and religious mix of the population, nor is it linked to any ascertainable pattern of social or other deprivation. It is the result of the ruthless ambition of one man. The real losers in this case are the citizens of Tower Hamlets.”

Mawrey said the effect of his ruling was that “Mr Rahman’s election as mayor on 22 May 2014 was void – that is to say, it is as if it had never taken place”.

Rahman’s election agent, Alibor Choudhary, was also banned as a councillor with immediate effect.

The petitioners were praised by the judge for their courage and told that they had been fully vindicated.

They called for a criminal inquiry into Rahman but questioned whether it could be carried out by local police because of their “connections” to Rahman.

Azmal Hussain, a petitioner who said he would have lost his Brick Lane businesses if they had lost the case, dismissed concerns that the judgment would be seen as racist.

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“The people who have really suffered are ordinary people of all races who were supposed to accept corruption because it comes from someone claiming to be against racism. It is corruption, pure and simple, and it should be challenged,” he said.

During the hearing, the court heard evidence from a handwriting expert that hundreds of ballot papers carried marks suggesting they could have been filled out by the same person.

Rahman was also accused of making false statements about the personal character of Biggs by branding him a racist. “No rational person could think Mr Biggs was a racist – it was a deliberate and dishonest campaign. Rahman and Choudhary are personally guilty,” said the judge.

The judgment also found Rahman to be the first person since the 19th century to be found guilty of the misdeed of unlawful religious influence.

As the then mayor campaigned for re-election, local Muslims were told “that it was a religious duty to vote for Mr Rahman”, the judge said.

It was claimed that a Bengali newspaper, the Weekly Desh, published a letter signed by 101 Islamic leaders, which was “intended to have undue influence on the Muslim population of the borough”.

Mawrey also said “bribery” had been “proved” following an examination of grants in the borough. He said the “administration of grants” had been “firmly in the personal hands of Mr Rahman” and “cronies”.

“In administering the grants policy, Mr Rahman acted in total disregard of the council’s officers, its members and, almost certainly, the law,” he said.

Allegations of intimidation at polling stations fell “just short” of being proved beyond reasonable doubt and so Mawrey rejected them “with considerable misgiving”.

Yet he found that the behaviour of Rahman’s supporters had been “deplorable, even indefensible”.

Police had failed to spot obvious intimidation on election day, the judge said. He suggested that “an unkind person might remark that the policemen … had appeared to take as their role model the legendary Three Wise Monkeys”.

In an unusual move, Mawrey said that he was sure that the Law Commission would take a close look at the judgment as it weighed up possible reforms to electoral law.

The judge will also report Rahman to the Solicitors Regulation Authority which could lead to further action that may result in his suspension as a solicitor.

The director of public prosecutions will consider the evidence in the case, raising the prospect of a criminal investigation into the poll.